With the center curves cut, the ribs are bent and glued into place. Then the outer curves on all 6 blocks get shaped.
Here the upper ribs are shown glued and clamped.
And this is the lower ribs glued and clamped. Note that the ribs run long out the ends.
After all the glue has set, clamps can be removed and the corners trimmed to shape.
Using the old No. 5 to take the thickness of the willow down to 2 mm. After that, I cut to about 10 mm, square down to 8 mm or so, then bend to shape for linings inside the ribs.
Clothes-pin-and-rubber-band clamps (just like Stradivari! :-) ) to hold the linings in place while the glue dries.